This invention relates to signal alignment techniques and more particularly to systems and methods for aligning signals having different phases so that a given goal can be achieved by the aligned signals.
Currently multiple vectors are phase aligned by measuring the phase of each vector separately and adjusting each vector to a reference phase. To perform this alignment, the phase of each vector must be measured relative to a reference phase. Phase is a difficult measurement to make, and since each vector is measured separately, any errors in the phase measurements of the separate vectors add when the vectors are combined.
One system for using such an alignment technique is the above-identified patent application entitled SYSTEM AND METHOD FOR FULLY SELF-CONTAINED CALIBRATION OF AN ANTENNA ARRAY, Ser. No. 09/092,429 filed Jun. 5, 1998, now U.S. Pat. No. 6,133,868.
In any system where there is a need for an alignment of signals having different phases, there is usually limited isolation between the different input signals and the resultant signal thus bears a complex relationship to the input signals depending on the degree of interference therebetween. Typically, the errors will occur due to the fact that when more than one vector is present, the vectors that were measured separately will shift in phase due to the coupling of the other vectors. In this situation, a vector is defined as an input signal having a particular phase.
Thus, there is needed in the art for a system and method for aligning signals having different phases into a resultant signal combination having a certain characteristic all without directly measuring phase relationships.
There is a further need in the art for such a system and method which accepts a plurality of input vectors and adjusts the phase of each of the vectors, without making phase measurements, so that the resultant signal has a particular characteristic.
There is a still further need in the art for such a system where the outputs of the vectors are combined into a composite signal.
There is a still further need in the art for such a system in which the composite signal has the maximum signal strength and the phases of the individual vectors are adjusted to achieve such a maximum without measuring phase angles of the input vectors.
These and other objects, features and technical advantages are achieved by a system and method which allows for the calibration of an output composite signal from a plurality of input vectors having different phases by phase aligning the input vectors without measuring phase angles. The system and method of the present invention measures the resultant amplitude of the composite signal as each vector is rotated in phase. When the minimum signal level is achieved by the rotation of a specific vector, that vector is reversed (rotated) 180 degrees, which then results in the composite signal having its maximum value for that vector.
This process is repeated, in turn, for each of the other input vectors until all of the vectors have been rotated, first to find the minimum signal and then reversed to maximize that vector""s contribution to the composite.
This process can be repeated as many times as necessary to achieve the desired degree of alignment error.
The importance of adjusting the phase becomes apparent from one example. Assume that it is desired to send a number of signals to a common point and the signals must pass through different cable lengths or paths before arriving at the destination. These signals then will arrive at the common destination point out of phase with one another in differing amounts. In such a situation it would be desirable to adjust the phase of each of the inputs so that the common output is as close to being in-phase with each other as is possible regardless of the interference and interaction between the cables (paths) and without knowing ahead of time what the various phase affecting characteristics are.
Therefore it is one technical advantage of my invention that the composite signal is achieved by aligning the input vectors without measuring phase angles.
Another technical advantage of my invention is to achieve the desired result without storing calibration data from each individual vector.
Another technical advantage of my invention is to achieve the desired result by only measuring output relative magnitudes in a recursive manner.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.